We propose to continue our studies at the molecular level to determine the block(s) to human adenovirus multiplication in monkey cells. This block affects viral lac gene expression and results in a 2-7 fold reduction in the synthesis of most of the viral late proteins. A similar reduction in both the steady state levels and rates of synthesis of the corresponding mRNAs suggests that part of the block is due to defective transcription from the adenovirus major late promoter. We would like to know whether initiation of transcription and/or post-initiation processes are affected. Both transcriptional initiation and elongation will be analyzed. In addition, the factor(s) responsible for the different rates of transcription from this late promoter in abortively vs productively infected monkey cells will be sought using i) soluble, whole cell transcription extracts, ii) lysolecithin permeabilized nuclei or whole cells, and/or iii) infusion of viral or cellular components into intact, infected monkey cells with liposomes or by pinocytosis. In contrast to the situation found for most viral late proteins, the reduction in fiber protein synthesis cannot be accounted for solely by reduced RNA concentrations. Fiber synthesis is diminished 100-1000 fold even though the level of fiber RNA in abortive infections is approximately 10% of that seen in productively infected monkey cells. Furthermore, this residual fiber mRNA is present on polysomes in vivo and is efficiently translated in a reticulocyte cell-free system. We wish to distinguish between the following three possibilities: i) fiber protein is made efficiently in abortive infections but is rapidly degraded, ii) it is inefficiently synthesized due to a specific defect in the translational apparatus of the monkey cell, or iii) it is inefficiently synthesized because the mRNA is improperly "wrapped" with proteins so that a less functional mRNP particle is formed in vivo. Immuno selection of polysomes engaged in fiber synthesis and analysis of fiber production from endogenous mRNP in cell-free translation lysates prepared from infected monkey cells are two of the several approaches we will employ in order to decide between the above possibilities.